This invention relates to graphics display units and more particularly to method and apparatus for rapidly filling predetermined areas of a graphics display screen with predefined repetitive patterns which generally are relatively small in size compared to the total area to be filled with the pattern.
The filling of such predetermined areas of a graphics display screen with one or more preselected patterns, of itself, is well known. Generally, however, existing arrangements are relatively quite slow in "painting" the patterns and require additional or special circuitry and storage capacity which add significantly to the cost of such displays. Moreover, in such arrangements replicating patterns generally involves considerable shifting, splitting, and partial word writes.
What is needed is to be able to rapidly fill the predetermined areas of the screen without the requirement for substantial additional or special circuitry and memory and electronic manipulation required of prior art arrangements. According to the present invention, this problem is solved by effectively utilizing extra scan lines of the frame buffer memory, i.e., the lines of the frame buffer memory not being displayed on the screen, to house the patterns to be utilized in filling the predetermined shapes or areas, by first replicating those patterns as necessary in the undisplayed portion of the frame buffer memory, and utilizing portions of these stored patterns which coincide in at least one dimension with the shape(s) or area(s) to be filled, wherein the latter become filled one scan line at a time. Thereby, only the height of the patterns, as opposed to the areas to be filled-in per se, is required to fit in the height of the undisplayed section of the frame buffer.
In accordance with the invention, therefore, there is provided a method for rapidly filling-in predetermined shapes or areas of a graphics display image with one or more predefined patterns, comprising:
(a) providing a frame buffer with a first section for receiving the information constituting the image to be displayed and a second section for receiving one or more patterns to be utilized in filling the predetermined shapes of the image being displayed; PA1 (b) defining at least one replicatable pattern to be utilized to fill said predetermined shapes; PA1 (c) entering the pattern information of said at least one pattern into said second section of the frame buffer; PA1 (d) replicating said pattern throughout the memory locations of said second section comprising the scan lines associated to the block of memory locations into which the pattern is entered initially; and PA1 (e) filling in one or more shapes of the image being displayed with said at least one predetermined pattern replicated in said frame buffer second section.
Also in accordance with the invention, there is provided apparatus for performing the aforementioned method which includes means for selecting a portion of the replicated pattern to fill a section of the shape to be filled such that said portion of the replicated pattern and said section of the shape coincide in at least one dimension of the frame buffer memory .